Load estimation is the problem of estimating what fraction of the cell's available physical radio resources each user needs in order to meet its required Quality of Service (QoS). This may be different from the amount of resources it is currently consuming. Load estimation is a prerequisite for many radio resource management functions, including call admission control, congestion control and load balancing (between cells). For example, when deciding on whether or not to admit a new bearer in a cell, the base station (or eNB (evolved NodeB) using LTE (Long Term Evolution) terminology) will estimate the current load of the cell and the load increase caused by the new bearer and will then make a decision of whether or not to admit the new bearer depending on available system resources. The task of estimating the current load and the load increase is not trivial and depends upon, among other things, the number of existing radio bearers and their class of service (guaranteed bit rates etc), the type of new bearer requested and channel conditions between the base station and the respective User Equipment (UE).
Similar requirements were defined for admission control in WCDMA (Wideband Code Division Multiple Access) communications systems. However, one of the difficulties in admission control for WCDMA is that the resource is interference based, meaning that the interference due to the introduction of a new bearer can potentially affect the quality of other bearers. As a result the power levels of other bearers may have to go up, causing further interference in a further set of bearers etc. Thus estimating the effect of a new bearer is an iterative process that continues until either the interference level converges (ie the desired qualities of all bearers are reached) or one or more bearers are dropped. The techniques used in WCDMA systems are not generally applicable to OFDMA systems.
US-A-2008/0080378 describes a technique that can be used to estimate the load in an OFDMA system for the purposes of admission control. The system maintains, for each class of service, an average block requirement for that class. When a new bearer is requested, the system determines the class of the requested bearer and then determines the number of required resource blocks from the stored data and then determines whether or not to admit the new bearer depending on whether or not the required number of resource blocks is less than the available number of resource blocks.